It is 129.
28 (add on the prime number 11)
17
27.
27, 26, 37, 37
The answer of 17 + 123 is 140 and then minus 50 is 90
17
29
10° 17′ 0″ N, 123° 54′ 0″ E10.283333, 123.9
16 (add 3 every time).
5x + 17 = 7x - 123 123 + 17 = 7x - 5x 140 = 2x x = 140 ÷ 2 x = 70
The next number is 27. Nice puzzle! The reason is on discussion page, for those who are still working on it.